1. Field of the Invention
The present invention relates to a mobile communication technology, and more particularly, to a method for estimating a Doppler frequency with phase information, thereby estimating a maximum Doppler frequency.
2. Discussion of the Related Art
According as frequency resource becomes important in mobile communication technology, adaptive receiver techniques have been paid much attention to an efficient usage of the frequency resource and a flexible resource management. There are a lot of factors to optimize a performance of the adaptive receiver. Above all, to estimate a maximum Doppler frequency is one of the most valuable factors. The maximum Doppler frequency has been estimated according to the variation of the measured pilot signal strength. However, the method for estimating a maximum Doppler frequency may have errors in case of that the adaptive receiver has a great Gaussian noise or a very high Doppler frequency.
In a communication system using a Phase Shift Keying (PSK) modulation of a non-coherent method, a maximum Doppler frequency is also estimated based on variations of the received signal strength. Particularly, in case of a communication system using Differential Phase Shift Keying (DPSK) modulation, because a pilot signal is not transmitted to a receiver, the receiver may estimate a maximum Doppler frequency using variations of another received signal such as traffic signal.
However, if the aforementioned method for estimating the maximum Doppler frequency with variations of a power for the received signal is applied to CDMA system using a rapid closed loop power control method, it has problems decreasing an accuracy in the estimating of a maximum Doppler frequency.